Lighting system for a stereomicroscope

ABSTRACT

Illumination arrangement for a stereo microscope, preferably a Greenough type stereo microscope, comprising at least one, preferably two illumination channels which are arranged in a plane which is arranged essentially orthogonally with respect to the plane of the two observation channels, preferably with two light channels in the interior of the microscope housing outside of the observation beam paths, wherein the light channels are guided around the observation optics.

[0001] In stereo microscopy, external incident illumination arrangementsin which direct illumination is arranged outside the microscope basebody belong to prior art.

[0002] Such arrangements can be halogen lamps with reflector mirrorswhich are fastened to the stereo microscope support, to the pillar or tothe stereo microscope base body itself and enable oblique incidentillumination.

[0003] Cold-light illumination arrangements which are arranged, forexample, at the pillar or at the stereo microscope support are known andare constructed, for instance, as flexible or semirigid one-armed ormultiple-armed light guides with focusing optics. Without fastening tothe stereo microscope base body or to the stand, there are one-armed ormultiple-armed, semirigid goosenecks, as they are called, which arefastened exclusively to the cold-light source and can be optionallypositioned spatially.

[0004] Further, cold-light ring lamps which are attachable to the frontarea of the stereo microscope are known and available, e.g., as 4-pointring lamps or slit ring lamps in different diameters and radiatingangles. All of these external incident illumination arrangements ensurea highly differentiated incident illumination, i.e., the object examinedthrough the stereo microscope can be optimally illuminated correspondingto its surface structure and spatial extension. A disadvantage in theseexternal illumination arrangements is that they sometimes occupyconsiderable space in the object region, i.e., direct viewing of theobject and free space for manipulation is sometimes severely limited.

[0005] A further disadvantage in these external illuminationarrangements consists in that when the stereo microscope is fastened inspecial stands (e.g., machine holders, floor or wall stands) and as aresult of the free spatial positioning of the stereo microscope whichthis involves, the light must first always be “tracked” separately(insofar as the illumination arrangement is not fastened to the stereomicroscope base body itself). The disadvantages mentioned above can beavoided if the illumination arrangement itself can be successfullyintegrated in the stereo microscope base body in a suitable manner so asto save as much space as possible.

[0006] A number of different suggestions for solving this problem, someof them already published, with the aim of suitably integratingillumination systems directly in optical instruments (for example, inphotographic cameras, video cameras, camcorders, microscopes, stereomicroscopes, operation microscopes) are known internationally.

[0007] In stereo microscopy, internal incident illumination arrangementsin which the light is coupled into (coaxial incident light principle)the observation channels via suitable beam splitting elements (prisms,splitter mirrors) inside the microscope base body are known from theprior art. In this connection, light can be generated by a conventionalmicroscope incident light arrangement or via a cold-light source andlight guides and can be transported until it is coupled into theobservation channels via the above-mentioned beam splitting elements atdifferent locations (e.g., above or below the stereo microscopepancratic or zoom system). Aside from the above-mentioned coaxialillumination arrangements which are fixedly integrated in the stereomicroscope base body, there are also modular units which can bearranged, for example, in such a way that they can be divided betweenthe stereo microscope pancratic system and the main objective (e.g.,Zeiss telescope type stereo microscope with modular coaxial illuminationdevice and flexible light guide input coupling, light guide connectionto Schott cold-light source KL 1500). An advantage in the coaxialillumination arrangement is that the light is “guided along” with thestereo microscope base body and, in case of internal coupling in abovethe stereoscopic pancratic system, that there is an exact adaptation ofthe object field during zoom magnification. With internal coupling inbelow the stereoscopic pancratic system, the size of the illuminatedobject field is constant and is designed for the maximum object fieldthat can be achieved with the pancratic system. A disadvantage in all ofthe above-mentioned arrangements with the coaxial incident lightprinciple is the occurrence of strong reflections—especially with highlyreflective object surfaces—and a resulting deterioration in imagecontrast through the coupling of light into the observation channels.The various possible arrangements for suppression of reflections withpolarizing-optical means (e.g., antireflection device for Zeisstelescope type stereo microscopes) are also prior art. Known reflectionsuppression arrangements with polarizing-optical means have their owndisadvantage in that a considerable reduction in illumination intensityoccurs due to the high absorptive power of the at least two polarizingfilters that are required. Other internal incident illuminationarrangements which are modified from this basic principle and employedin telescope type stereo microscopes use only the front main objectivefor coupling light into the observation beam paths or into an azimuthalplane of incidence different from the observation channels. In thesearrangements which are modified from the basic principle, there alsoremains the problem of the formation of reflections and eliminationthereof with polarizing-optical means. In stereo microscopy, the coaxialincident light principle is preferably applied only with planar or flatspecimens (shallow depth of field) because, with this verticalillumination, only a poor contrast or a poor spatial visual impressioncan be achieved in case of objects with depth of field or objects withsurface relief; a substantially improved contrast and spatial impressioncan be achieved by the shadow effect occurring with obliqueillumination. The different internal illumination arrangements workingin accordance with the coaxial incident light principle which weredescribed above are used in conventional stereo microscopes (telescopetype construction), operation microscopes, in medical equipment withstereoscopic observation (colposcopes, slit lamps) or sometimes inendoscopes.

[0008] The laid open application DE 196 40 352 A1, “InternalIllumination Device and Video Microscope System”, describes anarrangement for coupling in light via beam splitting as is known inconventional brightfield incident light microscopy. Another arrangementprovides integration of direct illumination (lamp with reflectormirrors) in a video device; in this case, light is transmitted via lightguides into the object space with oblique illumination and there is arepeated coupling of light into the observation channel by light guidesvia beam splitting (coaxial incident light principle). The proposedintegrated illumination arrangements which are known in part from theprior art are directed only to the combination of video microscopesystem with video equipment.

[0009] U.S. Pat. No. 4,783,159, “Operation Microscope”, describes atelescope type operation microscope with an integrated internalillumination arrangement for illuminating the operating field. In thisconnection, the light is principally coupled in between the zoom system(pancratic system) and the main objective. The illumination system whichis separately constructed in the operation microscope illuminates theoperating field via the following optical elements: light guide→separatezoom system→projection lens→main objective. Through the use of differentoptical deflecting elements (reflection prisms), it is possible toilluminate the operating field via the main objective at differentlocations (axially or extra-axially, as desired), resulting indifferentiated illumination of the operating field (e.g., the eye).

[0010] Patent EP 0 793 128 A1, “Illumination Structure in Microscope”,describes a microscope (stereoscope in a parallelconstruction/macroscope) in which an internal illumination system isarranged behind the objective. Different arrangements are described bywhich light can be coupled in behind the objective, for example, on theoptical axis of the objective between the observation channels (twopairs) with one illumination channel, between the observation channelpairs with two or more illumination channels, or coupling in light usingareas of the observation optics separated by mounts.

[0011] Patent DE 39 06 555 A1, “Incident Light Object IlluminationDevice”, describes an (external) illumination device which is arrangedat an observation device and which comprises a plurality of individuallight sources (e.g., self-luminous objects, glass fibers orback-lighting diaphragms) which are also switchable individually andwhich are arranged in an at least two-dimensional array whose centercoincides with the optical axis of the observation imaging optics.

[0012] The patent “Epidark Illumination System” DE 39 29 768 A1describes an Epidark illumination system, preferably for reflected lightmicroscopes, in which light coming from a light source is guided betweena sleeve and an objective lens for illuminating an object (arrangementsimilar to that in incident light darkfield arrangements). A very flatillumination of the object field can be achieved with this ring-shapedillumination arrangement.

[0013] Patent EP 0 50 940 A2, “Microscope Illuminating Apparatus”, showsdifferent microscope illumination arrangements for incident lightbrightfield and darkfield illumination and for transmitted lightbrightfield and darkfield illumination in which the coupling of lightinto the illumination-optical systems is carried out by fiber-opticsamong other means.

[0014] Patent DE 19523712 A1, “Stereo Microscope”, describes a stereomicroscope (telescope construction) which has an observation front lensand an illumination lens that are separate from one another. A beam ofobservation light emitted by an object point is directed parallel by thefocusable front observation lens. The illumination lens projects a beamof illumination light onto the object point. A position to beilluminated can be changed corresponding to the movement of an objectpoint by the arrangement/focusing of the observation and illuminationlens. It is the object of this special arrangement to achieveillumination which is as coaxial as possible, i.e., to adjust thesmallest possible angle between the optical axis of the illuminationlight and optical axis of the observation light (prevention ofreflections).

[0015] It is the object of the invention to realize the illuminationarrangement for stereo microscopes so as to have a minimum spacerequirement, but in such a way that the basic optical-mechanicalconstruction is influenced only minimally and a bright, homogenous andreflection-free illumination of the maximum visible object field is madepossible independent from the position and observation direction of thestereo microscope.

[0016] This object is met through the features of the independentclaims. Preferred further developments are the subject matter of thedependent claims.

[0017] The invention will be explained more fully in the following withreference to the schematic drawings.

[0018]FIG. 1 shows a bottom view of a stereo microscope according to theinvention;

[0019]FIG. 2 shows the light guide used according to the invention;

[0020]FIG. 3 shows a schematic side view in section;

[0021]FIG. 4 shows a side view vertical to the side view according toFIG. 3;

[0022]FIG. 5 shows advantageous possible adjustments for illumination;

[0023]FIG. 6 shows an arrangement for contrasting, for example,fluorescence excitation via the spot illumination device.

[0024] An arrangement satisfying the objective stated above is achievedin that a fiber-optic illumination arrangement which is completelyseparate from the observation beam paths and has focusing optics isintegrated in the stereo microscope base body, preferably through thearrangement of two spots in a plane orthogonal to the observation plane.

[0025] In FIG. 1, B1 and B2 represent the outlet openings or objectiveends of two observation channels of a Greenough stereo microscope MI inthe direction of the object. The microscope MI is connected with a standS by a microscope support MT. The outlet openings BL1, BL2 of two lightsources are arranged vertical to the connecting axis of the observationchannels.

[0026] As a result of this orthogonal arrangement of the illuminationchannels, a bothersome imaging of the illumination channel afterreflection in the object plane (critical in the case of highlyreflective objects) in the second observation channel and a resultingdeterioration in contrast are prevented. Further, in order to preventreflections in the entire stereo microscope zoom range in case of highlyreflective objects and to improve stereoscopic contrast, theillumination arrangement, as is shown in FIGS. 4, 5, is advantageouslyarranged at an angle ≠0°, i.e., at an angle of≈10° . . . 12°(≡half-angle to center) to the optical axis of the microscope. Focussingoptics FO which are arranged in front of the light guides and whichlight the object plane can be constructed as stationary systems(lighting of the maximum object field diameter) and, in principle, alsoas zoom systems (e.g., mechanically coupled with the observation zoomsystem) with variable object field diameter.

[0027] In order to achieve a maximum illumination intensity in theobject plane, it is advantageous when the illumination is carried outvia a twin light guide LL (see FIG. 2) provided with focusing optics FOand a superposition of the two individual spots takes place in theobject plane. The two individual fiber bundles of branch V of theflexible twin light guide LL are joined inside the stereo microscopebase body and exit as a continuous (prevention of light losses) one-arm,flexible light guide—provided with a sufficient length—via a strainrelief ZE at a suitable location on the stereo microscope base body. Thelight guide is then connected with an external cold-light source LQ viaa standardized end piece ST. Glass light guides or plastic light guidesor fluid light guides (especially advantageous in fluorescenceillumination arrangements—see also FIG. 6) can be used as flexible lightguides.

[0028] A possible arrangement of the integrated fiber-optic illuminationarrangement in a Greenough type stereo microscope in a plane parallel tothat of the observation channels (sectional view through an illuminationchannel) is shown in FIG. 3. The microscope MI is only indicated indashed lines without the tube. The light guide LL is coupled into themicroscope housing from above and has a strain relief ZE. Its branchedpart V advantageously extends entirely in the interior of the microscopehousing between the lens groups L of the zoom system of the microscope;these lens groups L are movable on guides F and are partially stationarywithout the observation beam paths being vignetted in this way.

[0029]FIG. 4 shows that the two light guide ends provided with focussingoptics FO form an angle to the optical axis of the microscope andaccordingly advantageously overlap with respect to their illuminationspots BS, so that a uniform bright illumination of the object in theobject plane OE is achieved over the entire maximum object field OF.

[0030] This illumination principle is suited to Greenough type stereomicroscopes and, in principle, for telescope type stereo microscopes. Inorder to prevent reflections (disadvantage of the known coaxial stereomicroscope illumination arrangements), illumination can also be realizedoutside of auxiliary lens systems (Greenough systems) and objectives(telescope systems, typical illumination arrangements for operationmicroscopes). A stationary installation of the illumination focusingoptics provides optimal illumination of the object field for the stereomicroscope without an auxiliary system (Greenough construction) or onlyfor an auxiliary system/objective. A displacement and swiveling of theillumination focusing optics by mechanical guide elements and adjustingelements is required for adapting to different objectives/auxiliarysystems). This is shown in FIG. 5.

[0031] Illumination optics FO which can be swiveled, displaced radiallyand focused in different directions via operator controls are shownhere. The illumination focusing, i.e., the variable adaptation of theillumination spot to the observable object field diameter, is realizedby a focusing control FS which is either mechanically coupled with theobservation zoom system or is carried out electronically via motor.

[0032] Different advantageous variants are described in the following:

[0033] A swiveling of the illumination focusing optics (varying theangle of incidence of the light spots in connection with B), actuationby suitable external operator controls;

[0034] B radial displacement of illumination focusing optics (varyingthe angle of incidence of the light spots in connection with A),actuation by suitable external operator controls;

[0035] C varying illuminated object field diameter by focusing; varyingthe distance between the light guide output and focusing optics withmanual actuation or light-guide coupling into a separate illuminationzoom system which is positively coupled mechanically with theobservation zoom or is actuated by a motor-driven external control FS.

[0036] For this purpose, the illumination focusing system canadvantageously be coupled with the zoom drive of the stereo microscopemechanically or electrically, i.e., the illuminated object fielddiameter is automatically variably adapted with actuation of theobservation zoom system.

[0037] This illumination principle is also suitable for microscopycontrast methods. FIG. 6 shows an arrangement for fluorescenceexcitation via the spot illumination device by way of example. Based onthe arrangements described in FIG. 4 or FIG. 5, fluorescence excitationvia the spot focusing optics is possible when a filter holder FAA forreceiving and changing filters is switched between the light guide endpiece ST and the light source LQ in fluorescence excitation forreceiving and changing excitation filters A (this filter changinglocation is already present in many commercially available lightsources, especially cold-light sources). Further, when a filter holderfor blocking filters FAS is accommodated in the observation channels forchanging blocking filters S, very good stereoscopic fluorescencecontrast can be achieved in observation, i.e., high-contrast,reflection-free observation is possible in oblique illumination by meansof a complete decoupling of illumination channels and observationchannels. Suitable light sources for fluorescence excitations in thevisible spectral range are halogen cold-light sources (e.g., Schottcold-light source KL 1500) or XBO (xenon very-high-pressure lamps, e.g.,XBO 75 W); for UV fluorescence excitations, HBO (mercuryvery-high-pressure lamps, e.g., HBO 50 W or HBO 100 W) are suitable. Alarge number of different filter sets (comprising excitation filters andblocking filters) are offered by filter manufacturers and stereomicroscope manufacturers for a wide variety of different applications influorescence stereo microscopy. The coupling in of light via lightguides is advantageous for stereo microscope observation in any spatialdirection (e.g., special stands for conservationists) with fluorescenceexcitation because the above-mentioned very-high-pressure lamps with arigid coupling to the stereo microscope without light guides would bebothersome for the observer because of its considerable heat development(risk of burn injury when touched); moreover, according tomanufacturer's instructions, the very-high-pressure lamps may only beoperated in a vertical setup position (these lamps are destroyed whensharply inclined). In the arrangement according to the invention shownin FIG. 6, the light source can remain at a stationary location (forexample, fastened to the special stand) and the stereo microscope can bespatially oriented in any manner such that it is connected with thelight source via the light guide.

[0038] Trial Results

[0039] Incident illumination as shown in FIG. 1 to FIG. 4 is integratedin the Zeiss Stemi 1000 base body while maintaining a working distanceof 4″ (110 mm). The two illumination optical systems—arranged in anorth-south direction—were positioned at an angle of 2×8° to realize anoblique incident illumination with extensive decoupling of theobservation channels. An image quality which is substantially improved(no bothersome incident light reflections in the upper zoom area) overcostly coaxial incident illumination arrangements (minimizing ofreflections with polarizing-optic means) was achieved with thisarrangement.

[0040] The following performance features were determined in theprototype:

[0041] a) Bright, homogeneous lighting, illumination with Schott KL1500e cold-light source; an illumination angle of 2×8° was realized inthe prototype; in this way, it was possible to achieve an illuminationangle which was substantially smaller than with externally mountedlighting with highly inclined incident light (e.g., Schott point lightor ring light: 18°, light 10: 35°).

[0042] b) Substantially higher-contrast illumination compared withconventional coaxial illumination arrangements with beam splitting(illumination angle 0°, problem of lightening single-reflections whichcannot be entirely eliminated in spite of antireflection arrangement)through complete separation of observation and illumination beam paths.

[0043] c) By means of complete integration of illumination in the stereomicroscope base body, the full working distance (4″ with Stemi 1000) isretained: advantage over externally mounted cold-light components bywhich the working distance is limited and direct, free viewing ofobservation object is obstructed.

[0044] d) All external stereo microscope interfaces are retained (Ø76 mmas internationally standardized receptacle—Ø, receptacle—Ø for externalcold-light components, coupling thread for auxiliary systems),accordingly, there are no limitations with respect to the variabilitywhich has been achieved.

[0045] e) By means of integration, illumination does not need to betracked in case of changing observation locations (e.g., special standsfor MEG applications, scanning of large object fields with cantileverstands, e.g., in textile industries, restoration or conservation standswith optional spatial orientation of the stereo microscope base body)and free viewing of the object was retained.

[0046] In view of the extremely confined basic construction of thestereo microscope, the following alternatives are seen for modifying theabove-mentioned embodiment examples (FIG. 1 to FIG. 4) with necessarydesign limitations for spot illumination:

[0047] omission of an illumination channel, illumination only with aspot from north or south direction;

[0048] instead of a flexible light guide, a light-conducting rod orinternally coated light-conducting tube could also be used, at which aflexible standard light guide (e.g., for KL 200) can be coupled in atthe upper end so as to be exchangeable (an advantage in case ofreasonable transmission losses);

[0049] omission of focusing optics, i.e., an object field of≈160 mm isilluminated (relatively homogeneous illumination≈Ø100 mm) by means ofthe high light guide aperture (A≈0.66 with A2 type fiber) at a freeworking distance of 90 mm; the visible illumination intensity in theviewing field, particularly in the upper zoom area, is then appreciablylower than with an adapted illumination of the object viewing field, butit is still judged sufficient (advantage of large-area illumination ofobject field with object manipulation and object positioning with thenaked eye, i.e., the light is stilled delivered by the Stemi).

1. Illumination arrangement for a stereo microscope, preferably aGreenough type stereo microscope, comprising at least one, preferablytwo illumination channels which are arranged in a plane which isarranged essentially orthogonally with respect to the plane of the twoobservation channels.
 2. Illumination arrangement according to claim 1in a Greenough type stereo microscope with two light channels in theinterior of the microscope housing outside of the observation beampaths.
 3. Illumination arrangement according to at least one of thepreceding claims, wherein the light channels are guided around theobservation optics.
 4. Illumination arrangement according to at leastone of claims 1 to 3, wherein the illumination direction is carried outat an angle to the optical axis of the microscope, so that no directlight falls in the observation channels.
 5. Illumination arrangementaccording to at least one of the preceding claims, wherein theillumination is carried out via at least one light guide. 6.Illumination arrangement according to at least one of the precedingclaims, wherein the light guide is a flexible glass light guide and/orplastic light guide and/or fluid light guide.
 7. Illuminationarrangement according to at least one of the preceding claims, whereinthe light guide extends at least partially in the interior of themicroscope housing.
 8. Illumination arrangement according to at leastone of the preceding claims, wherein the illumination is carried out viathe light guide ends.
 9. Illumination arrangement according to at leastone of the preceding claims, wherein the illumination is carried out viaillumination optics arranged following the light guide end. 10.Illumination arrangement according to at least one of the precedingclaims, wherein the illumination optics are arranged so as to beadjustable and/or displaceable and/or swivelable with respect to theimage scale as zoom system.
 11. Illumination arrangement according to atleast one of the preceding claims, wherein a hand-actuated and/ormotor-operated control is provided for adjusting the illuminationoptics.
 12. Illumination arrangement according to at least one of thepreceding claims, wherein, when the illumination optics are adjusted asa zoom system, this adjustment is coupled to the adjustment of themicroscope zoom system.
 13. Illumination arrangement according to atleast one of the preceding claims, wherein the illumination is carriedout via a light guide which branches to generate the two light channels.14. Illumination arrangement according to claim 13, wherein thebranching takes place entirely within the microscope housing. 15.Illumination arrangement according to one of claims 13 or 14, whereinthe branches of the light guide are guided around the observationchannels.
 16. Illumination arrangement according to at least one of thepreceding claims, wherein the light guide is connected with a cold-lightsource arranged outside of the microscope.
 17. Illumination arrangementaccording to at least one of the preceding claims, wherein afluorescence excitation is carried out via the illumination channels.18. Illumination arrangement according to claim 17, wherein at least onelight guide is connected with a light source which is arranged outsideof the microscope and which is suitable for fluorescence excitations incombination with exchangeable excitation filters.
 19. Illuminationarrangement according to one of claims 17 or 18, wherein a filter holderfor excitation filters is provided between the light source and thelight guide and a filter holder for blocking filters is provided in theobservation beam path.